Response willingness is an essential ingredient of healthcare system capacity across the all-hazards spectrum. Our pandemic influenza-focused results in this study reinforce a critical finding from previous LEADS-based research on U.S. EMS workers' response attitudes toward non-pandemic influenza scenarios – namely, that the willingness of these workers to fulfill response roles during large-scale public health crises cannot be universally assumed 
. With minimal regional variation, overall 12% of the workers in our study would not voluntarily report to duty in a pandemic influenza emergency when asked, and 7% of the workers would not report to duty even if required.
Of concern, our study revealed that the majority (52%) of EMS workers would stay home if a risk of disease transmission to family existed. This was the case irrespective of knowing one's role or recognizing its importance, contrary to previous research that showed that the perception of the importance of one's role in the agency's response and understanding one's role-specific response requirements were among the leading predictors of willingness to respond for local health department workers 
. As such disease transmission risk always exists in an influenza pandemic, this finding has significant operational implications not only for EMS, but also for the overall healthcare system response infrastructure as a consequence. Further, mobilizing EMS personnel to particularly hard-hit communities during a pandemic will not be easy. We found that 20% of the respondents would be reluctant to do so, even if they thought the probability of becoming ill was low. Since an influenza pandemic can be expected to exert disparate surge capacity demands on different communities at varying times, this finding represents a substantial EMS challenge to be tackled.
During the global emergence of a novel influenza strain, already spreading rapidly in the US throughout the survey window and declared a pandemic by the WHO on 11 June 2009, less than half (43%) agreed that this event would occur in the community they serve, and only 66% agreed that a pandemic influenza event would have severe public health consequences. These responses may likely have reflected that the inevitability of the strain's dissemination and scope of impact had not been fully grasped by the public at that point.
Given previously-recognized EMS infrastructure challenges 
and amidst a highly contagious strain, our study's findings present a problematic landscape for prehospital healthcare system capacity in the current pandemic. However, our findings also simultaneously highlight opportunities for impactful interventions to boost pandemic influenza response willingness among this cadre of first responders. Consonant with past research on EMS workers' response willingness in terrorism scenarios 
, our findings reveal the importance of hazard-specific response education: knowing one's role in a pandemic more than doubled an EMS worker's likelihood of voluntarily reporting (unadjusted OR
2.3), while recognizing the importance of one's role increased such willingness more than six-fold (unadjusted OR
Additionally, our results indicate that emphasis on personal and family preparedness planning is strongly advisable in the context of pandemic influenza education for EMS workers. If the family is prepared to function in their absence, EMS personnel were more than twice as willing to mobilize to another, more severely affected community (OR
2.3), after adjusting for other attitudes and beliefs. These findings reinforce those of a UK study showing healthcare workers with caring responsibilities to be significantly less likely to report to work than those without dependents, and a study in the US in which over 20% of workers agreed that personnel without children should be the primary responders in a pandemic 
. Preparing families of healthcare workers, including EMS workers, will be critical in ensuring an adequate public health response in a pandemic emergency. Instilling confidence in occupational safety in an influenza pandemic also appears critically important for this healthcare provider cohort. EMS workers who were confident in their work environment safety in an influenza pandemic were more than three times as likely to voluntarily report to duty in such an event (OR
3.3), and were more than twice as likely to be willing to mobilize for response to another more severely affected community (OR
Importantly, our findings also suggest the relevance of the Extended Parallel Process Model (EPPM) to inform educational efforts that explicitly address EMS workers' perceptions of threat and efficacy toward pandemic influenza response. Those fitting a “concerned and confident” (high threat/high efficacy) EPPM profile were more than four times as likely (OR
4.7) to be willing to report to work if asked but not required, after adjusting for other covariates. This highest level of willingness among the “high threat/high efficacy” group is consistent with a pattern observed in earlier EPPM survey-based research we conducted on local public health workers' willingness to respond in an influenza pandemic 
. Moreover, consistent with that previous research, we found that perceived efficacy carried substantial weight among EMS providers: those fitting a “low threat/high efficacy” profile were still more than three times as likely (OR
3.7) to be willing to respond, after adjusting for other covariates. Nationally to date, healthcare workforce emergency preparedness trainings have focused nearly exclusively on cognitive (ability-focused) rather than affective (willingness-focused) domains of response. However, our findings highlight the need for enhanced attention to pandemic response-related attitudes in the context of EMS workforce trainings, and point to the EPPM as a potentially useful framework for informing these offerings.
Despite alternative terminology used in risk perception modeling, the identification of a simultaneous evaluation of affective and analytic processes in risk perception reinforces the use of the EPPM as a model of choice in informing pandemic-related educational efforts 
. One risk perception model describes the perceptual characterization of risk through two main axes: risk familiarity (unknown risk is perceived as higher risk) and level of dread associated with risk 
. Similar to the EPPM in which threat and efficacy are simultaneously evaluated, this risk perception model identifies a parallel interplay of logical and emotional processes 
. In the context of the risk-benefit paradigm, an individual decision is based on both thoughts and feelings. If the outcome of the decision is perceived to be emotionally positive, the risk will be viewed as low and the benefit as high, increasing the likelihood of the decision (action) 
. The critical importance of affective evaluations in this risk perception model underscores the relevance of attitudinal interventions as informed by the EPPM, for pandemic willingness-related response trainings for EMS personnel.
We noted that 41 percent of the EMTs and Paramedics who responded to this survey did not receive an influenza immunization in the last 12 months. Since it seems likely that the same types of individuals who do not receive seasonal flu vaccination may also be negatively predisposed to pandemic H1N1 2009 influenza A vaccinations, we compared the characteristics of EMS personnel who received flu vaccinations with those who did not. Other than age (older EMTs and Paramedics were more likely to get vaccinated than younger ones), we were unable to identify any significant relationships between individual characteristics and vaccination propensities.
We also noted that 52 percent of the EMTs are in rural areas (that is, they do most of their EMT work in areas or towns with fewer than 25,000 people). These data are consistent with previous findings in the literature 
. However, as call volumes in rural areas are much lower than in other areas, this datum should not be interpreted to mean that 52% of the nation's EMS services are provided in rural areas.
Certain limitations to this study need to be acknowledged. First, the 49% survey response rate, while comparable to that of earlier research on willingness of U.S. EMS personnel to respond to terrorist incidents 
, may have introduced the potential for non-response bias in the current study. However, a high level of survey responder versus non-responder demographic similarity has been noted in previous LEADS cohort analyses 
. A second noteworthy limitation of the current study is that responses to a survey of this type may not necessarily predict actual behavior. Most studies to date linking healthcare workers' intention to their behavior have recognized methodological flaws including lack of experimental design, poor methods in measuring behavior, poor matching of the context of the intention with the behavior measured, and poor reporting of studies 
. Despite both limited quality and quantity of literature, a theoretical framework developed through a meta-analysis of 78 studies examining the effectiveness of social cognitive theories in explaining the relationship between intention and behavior presents intention – influenced by belief about consequences, social influences, moral norms, role and identity and characteristic – to be one of the most proximal causation factors to actual behavior. However, the accuracy of this behavior prediction decreases as the complexity of a situation and the number of modulating factors increases.. Although this meta-analysis did not look at the use of the EPPM as a method of predicting behavior or informing educational intervention, it highlights the ability of models, specifically the Theory of Planned Behavior (TPB), to predict behavior in healthcare workers 
. In the context of a pandemic, it is noteworthy that non-healthcare workers' actualization of their intended preventive and avoidant behaviors has been found to increase if there is a high level of associated anxiety, perceived susceptibility to or severity of disease, and perceived effectiveness of the behavior (response efficacy) 
. All of these factors would be heightened for EMS workers in the event of a pandemic, suggesting that their intentions may also correspond to their actual behavior in this situational context.
The LEADS snapshot survey for this study was developed in January 2009, prior to the earliest case identifications of H1N1 2009 influenza A virus; as a consequence, the survey did not explicitly refer to “pandemic H1N1 2009 influenza A” or “swine flu” in the context of its pandemic influenza questions. Although the survey was launched on May 15, 2009, the World Health Organization did not declare a pandemic until June 11, 2009, which was part of the survey window. However, it should be noted that as of the survey launch date, a total of 34 countries had officially reported 7,520 cases of H1N1 2009 influenza A infection to the World Health Organization, including 4,298 laboratory confirmed human cases and three deaths in the United States 
; additionally, on April 29, 2009, approximately two weeks prior to the survey launch date, the World Health Organization had already raised its pandemic alert level to Phase 5, signaling a pandemic was imminent 
. Finally, some of the demographic data used in the analyses came from the 2008 LEADS Survey, which was administered six months prior to this survey. Analyses of past LEADS Surveys indicate little change in these data (other than satisfaction with one's supervisor) over a 12-month period.
In conclusion, our study reveals the importance of underlying attitudes and beliefs that may substantially hinder willingness to report to duty among EMS workers in a global public health emergency. Given the “all available hands on deck” nature of pandemic influenza response, the results of our survey indicate that insufficient attention to these attitudinal domains of response can have a significantly detrimental impact on prehospital providers' capacity to meet surge challenges. Explicit attention to the realms of perceived threat and efficacy within EMS readiness trainings may serve to help overcome these identified attitudinal barriers, yielding an EMS workforce that is not only able to respond to a pandemic threat in requisite numbers, but willing to do so.